Adjustable-arm protractor.



H. B. HILL.

ADJUSTABLE ARM PROTRAGTOR. APPLICATION: FILED MAY 19, 1913.

l ,096, 1 O7, Patented May 12, 1914.

Ema/mm @OWWM f aw 35% -0unuum PLANOGRAPH conwAsnmu'roN D. c.

HARRISON B. HILL, OF EAST PROVIDENCE, RHODE ISLAND.

ADJUSTABLE-ARM PBOTRACTOR.

To all whomc't may concern.

Be it known that I, HARRISON B. HILL, a citizen of the United States, residing at East Providence, in the county of Providence, in the State of Rhode Island, have invented a new and useful AdjustableArm Protractor, of which the following is a specification.

The purpose of my invention is to provide a protractor adapted for use, either side uppermost, in conjunction with a T-square, and which can be easily and readily adjusted to and set at any desired angle; be convenient for dividing circles or duplicating angles; and which may be efiiciently used in the place and stead of the 4.5 and triangles ordinarily used by draftsmen.

To these ends my invention consists in the construction, combination and arrangement of parts hereinafter described, and illustrated in the accompanying drawings, in which,-

Figure 1 is a plan view of my protractor in its closed position. Fig. 2 is a plan view of the same in its open position, illustrating its use in conjunction with a drawing board and T-square. Fig. 3 is a sectional end view on line 33 of Fig. 1. Fig. 4 is a longitudinal section taken on line H of Fig. 2.

Like reference letters and numerals indicate like parts in the several figures of the drawings.

In the drawings, 1 represents one of the arms of my protractor, which I term hereinafter the stationary arm, and 2 represents the second arm, which I term the movable arm, pivoted at its rear end, as at a, to the rear end of the stationary arm 1. Said arm 1 is provided near its rear end, on its inner edge, with a shouldered recess 1 and said movable arm 2 is similarly provided with a corresponding shouldered recess 2 arranged and adapted, when the two arms are shut together, to register with the recess 1 (Fig. 1.). Said movable arm 2 is beveled on both sides of its upper edge 2 so that an inking pen may be used with the protractor.

The rear end of the stationary arm 1 is of circular form and is slotted to receive the circular rear end of the movable arm 2, pivoted therein, as shown and described. Said circular end of the arm 1 is provided on both sides with graduations indicating degrees, although in the drawings only one side of the arm is shown.

Specification of Letters Patent.

Application filed May 19, 1913.

Patented May 12, 1914:. Serial No. 768,655.

A thumb screw 3 positioned in the recess 1 of the arm 1 and tapped longitudinally through the shoulder of said recess serves by contact with the edge of the rear end of the arm 2 to lock the latter in its adjusted position. When the arms 1 and 2 are shut together, as in Fig. 2, the recesses 1 and 2 constitute a containing chamber for the thumb screw 3, which is of less cross-section than the arms land 2 so as not to interfere with the free movement of the protractor upon the drawing board. In other words the thumb screw lies wholly between the planes of the upper and lower sides of the two arms, and presents no obstruction to the use of the protractor either side up.

The outer edge of the arm 1 is squared so as to fit truly against the edge of the T- square T, when the latter is placed upon the drawing board B.

In the practical operation of my invention the protractor is laid upon a drawing board or table with the arm 1 parallel with and in contact with one edge of the T-squarc. The arm 2 is moved laterally away from the arm 1 until the desired angle, as indicated by the graduation upon the rear end of the arm 1, is described and the arm 2 is then looked in its adjusted position by turning the thumb screw 3 into contact with the for ward edge of the rear end of the movable arm 2.

I claim:

An adjustable arm protractor comprising a stationary arm having a rear, circular, slotted end provided with graduations indicative of degrees and said arm being provided with a shouldered recess on its inner edge adjacent said end, a movable arm pivoted in said slotted end and provided with a shouldered recess on its inner edge arranged and adapted to register with the recess in the stationary arm when the two arms are in closed position, and a thumb screw positioned in the first named recess and arranged and adapted by contact with the forward edge of the movable arm to lock the latter at any desired angle to the stationary arm.

HARRISON B. HILL.

Witnesses:

FRED L. OWEN, CHARLES A. JoNEs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. G. 

